I have an older SSD in my laptop full of static data, mostly FLAC and a few zip files, there's very few files less than 10MB and likewise writes are weekly rather than multiple per second. I'm reluctant to buy a new, legacy disk to get more space because I move the laptop round a lot and my experience with legacy disks and bicycles is that they are a bad combination.

Looking at "advantages of BTRFS" "different filesystems" and HowToGeek I can't help thinking that ext2fs is likely to be the most space-efficient filesystem. It's not journalling, which is good for this application, and it's ok with large files. I don't think speed actually matters here, since the SSD is wildly faster than the music player needs.

Is there a better filesystem for this than EXT2? Can I format an SSD as one of the read-only CDFS-style formats, and would that get me more usable space?

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    How much do you hope to gain by losing the journal? – muru Dec 17 '15 at 6:35
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    @muru I'd be happy with even 1%. I've already cranked back the reserved space to zero, because it's not a system disk. I'm on "squeeze every last byte", because the effort of doing that is a once-off thing paid back by another few music tracks. – Móż Dec 17 '15 at 6:42
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    A couple of journals I checked were 128 MB, so, I guess 1-2%?. You would be much better off freeing up reserved space in ext4. – muru Dec 17 '15 at 6:45
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    Way back when, it was possible to influence the number of inodes in the filesystem (at mkfs time), with mostly big files, you have fewer files, so you need fewer inodes. But I can't see that making a big difference. – Ulrich Schwarz Dec 17 '15 at 7:11
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    You may also want to consider Joliet (CDFS) or (I can't believe I'm saying this) FAT32. Both are pretty rudimentary filesystems that would waste space on silly things like journals :) – David King Dec 17 '15 at 14:30

Can I format an SSD as one of the read-only CDFS-style formats?

Yes. You can use mkisofs to write directly to your SSD, no existing filesystem or partition table necessary.

mkisofs -o /dev/sdg /path2musicdir

Then the block device (SSD) can be mounted the same as any other iso file

mount -o loop,ro /dev/sdg /mountpt

NOTE: Files need to be named in an 8.3 format, unless you use the Rock Ridge, Joliet, or HFS/Unix extensions, which presumably will take a few additional bytes (fewer files for the sake of intelligent file names.)

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